A liquid crystal display device typified by a liquid crystal display panel, a liquid crystal display module and so forth utilizes dielectric anisotropy, optical anisotropy or the like of a liquid crystal compound. As an operating mode of the liquid crystal display device, various kinds of modes are known, such as a phase change (PC) mode, a twisted nematic (TN) mode, a super twisted nematic (STN) mode, a bistable twisted nematic (BTN) mode, an electrically controlled birefringence (ECB) mode, an optically compensated bend (OCB) mode, an in-plane switching (IPS) mode, a vertical alignment (VA) mode, a multi-domain vertical alignment (MVA) mode and a polymer sustained alignment (PSA) mode. Characteristics as described below are required as common properties for any liquid crystal material, whatever mode the device applies.
The characteristics include:                (1) being stable to external environment factors such as moisture, air, heat and light;        (2) showing a liquid crystal phase in a wide temperature range centering on room temperature;        (3) having a low viscosity;        (4) allowing a decrease in driving voltage when the display device is driven;        (5) having an optimum value of dielectric anisotropy (Δ∈); and        (6) having an optimum value of optical anisotropy (Δn).        
However, no single compound satisfies all of the characteristics at present, and a liquid crystal composition prepared by mixing several compounds to twenty or more liquid crystal compounds is currently used for the liquid crystal display device.
A liquid crystal display device having a higher display performance in contrast, display capacity, response time or the like has been required in recent years. In order to meet the requirement therefor, a demand for a liquid crystal display device according to an active matrix (AM) mode as typified by a thin film transistor (TFT) mode is rising mainly in a field of a television, a viewfinder or the like.
A recent trend of development in the fields is focused on advancement of downsizing or portability of the liquid crystal display device, as seen in a television or a notebook-sized personal computer that is made portable by reducing a size and weight. For a liquid crystal material used in association therewith, a material having a low driving voltage is required, more specifically, a liquid crystal compound allowing a decrease in a threshold voltage, and a liquid crystal composition containing the compound and having a low threshold voltage is required.
As known well, a threshold voltage (Vth) is shown by the following equation (H. J. Deuling et al., Mol. Cryst. Liq. Cryst., 27 (1975) 81):Vth=π(K/∈0Δ∈)1/2 
In the equation, K is an elastic constant of a liquid crystal material, and ∈0 is a dielectric constant of vacuum.
As understood from the equation, two ways are considered to reduce Vth, namely, increasing Δ∈ or decreasing K. However, actual control of elastic constant K of the liquid crystal material is still difficult according to a current technology, and the requirement is ordinarily met by using a liquid crystal material having a large value of Δ∈. From such a situation, a liquid crystal compound having the large value of Δ∈ has been actively developed.
Representative examples of a liquid crystal material showing a positive value of Δ∈ for low voltage driving to be used for a liquid crystal display device having a TN mode or the like to be driven with TFT include compounds (A) and (B) as described below (see Patent literature No. 1, for example).
                wherein, in the formulas, R is alkyl.        
Both compounds (A) and (B) have a 3,4,5-trifluorophenyl group in a terminal position of a molecule, and are expected as a liquid crystal material for low voltage driving. However, a numeric value of Δ∈ (A: 8.3, (B): 12.8) is not sufficient enough, and even if the compounds are used, preparation of a liquid crystal composition that can sufficiently meet the requirement is considered to be difficult.
Moreover, as a mode for overcoming narrowness of viewing angle being a biggest problem of the liquid crystal display device, a new mode such as the IPS mode, the VA mode, the MVA mode and the OCB mode has been disclosed in recent years. Among the modes, in particular, devices according to the VA mode and the MVA mode have a wide viewing angle and also an excellent responsiveness, and further a high contrast, and thus development of such a mode is actively performed in each display manufacturer. Features of the liquid crystal composition used for the liquid crystal display devices according the modes include a liquid crystal composition having a negative value of dielectric anisotropy. As a compound showing a large negative value of dielectric anisotropy, compound (C) as described below is reported, for example (see Non-patent literature No. 1).

According to Non-patent literature No. 1, compound (C) shows a negative value of dielectric anisotropy (Δ∈=−4.1), but an absolute value of Δ∈ is small. Accordingly, the liquid crystal composition containing the compound is presumed to be difficult to meet the requirement of the VA mode or the MVA mode.
As described above, a liquid crystal compound having a large positive or large negative value of dielectric anisotropy (Δ∈), more specifically, a compound having a large absolute value of dielectric anisotropy (|Δ∈|) is eagerly awaited.